Action towards Limiting Total Nitrogen, Total Phosphorus, and Total Inorganic Nitrogen Loads from NPDES-Permitted Facilities

Photos of minimizing loads

About this indicator
Discharges from industrial facilities, especially wastewater treatment facilities, with little to no treatment for nitrogen and phosphorus are a significant source of these nutrients to surface waters throughout the country. Setting permit limits and treating the wastewater to meet these limits can substantially reduce nitrogen and phosphorus loading from these facilities, protecting local and downstream water quality. The data in this indicator are for major (≥1 million gallons/day (MGD)) and minor (<1 MGD) industrial and publically-owned treatment facilities with individual or general National Pollutant Discharge Elimination System (NPDES) permits that, based on their classification and corresponding typical effluent nutrient concentrations, are likely to be discharging nitrogen and phosphorus. Presented are the percent of such facilities that have permit limits (which include monitoring requirements), or monitoring requirements only, for total nitrogen, total phosphorus, and/or total inorganic nitrogen (ammonia, nitrate and nitrite).

State progress towards implementing total nitrogen (TN), total phosphorus (TP), and total inorganic nitrogen (TIN) National Pollutant Discharge Elimination System (NPDES) permit limits, or monitoring requirements only, for major and minor facilities likely to discharge nitrogen (N) and phosphorus (P).

                                            Major and Minor dischargers                                 Major dischargers only
State # of facilities likely to discharge N or P† % with TN limits % with TP limits % with TN monitoring only % with TP monitoring only % with TIN monitoring only # of facilities likely to discharge N&P † % with TN limits % with TP limits % with TN monitoring only % with TP monitoring only % with TIN monitoring only
Alabama 5,948 ‡ * 0% 8% 12% 21% 9% 191 ‡ 2% 7% 7% 92% 74%  
Alaska 1,200 0% 0% 4% 6% 0% 68 0% 0% 13% 44% 0%
Arizona 211 1% 3% 9% 39% 27% 75 4% 4% 4% 84% 75%
Arkansas 2,691 ‡ 0% 1% 9% 28% 1% 174 ‡ 0% 7% 15% 52% 9%
California 1,070 ‡ 0% * 0% 17% 26% 1% 237 ‡ 2% 2% 42% 78% 2%
Colorado 2,488 ‡ * 0% 1% 9% 19% 0% 114 ‡ 1% 10% 7% 76% 2%
Connecticut 200 5% 6% 36% 68% 0% 103 4% 6% 48% 84% 0%
Delaware 111 9% 14% 19% 26% 2% 21 29% 33% 48% 52% 0%
Florida 1,919 ‡ 7% 7% 11% 13% 4% 222 35% 38% 37% 46% 19%
Georgia 1,094 * 0% 9% 19% 40% 0% 196 1% 29% 8% 62% 2%
Hawaii 289 2% 2% 9% 9% 3% 17 6% 6% 94% 88% 47%
Idaho 453 ‡ * 0% 19% 14% 30% 5% 50 0% 22% 12% 74% 26%
Illinois 2,810 0% 2% 31% 56% 0% 269 0% 11% 28% 87% 0%
Indiana 2,756 * 0% 5% 9% 38% 1% 193 0% 20% 7% 74% 5%
Iowa 1,729 1% 0% 43% 44% 0% 124 2% 0% 77% 81% 0%
Kansas 1,357 ‡ * 0% * 0% 31% 32% 2% 54 ‡ 4% 0% 81% 100% 24%
Kentucky 5,130 * 0% 1% 9% 20% 0% 133 0% 17% 48% 74% 0%
Louisiana 7,750 * 0% * 0% 5% 7% 0% 327 1% 1% 35% 68% 1%
Maine 339 0% 7% 47% 55% 0% 75 0% 9% 77% 87% 0%
Maryland 2,350 4% 5% 9% 13% 6% 94 31% 60% 46% 22% 57%
Massachusetts 591 1% 14% 12% 17% 6% 119 3% 48% 38% 43% 23%
Michigan 1,297 0% 25% 12% 21% 0% 176 0% 70% 27% 22% 0%
Minnesota 858 0% 5% 30% 34% 2% 96 0% 43% 23% 55% 20%
Mississippi 3,756 1% * 0% 21% 30% 0% 96 7% 8% 59% 88% 1%
Missouri 10,675 ‡ * 0% 1% 9% 15% 1% 170 ‡1% 5% 32% 85% 7%
Montana 2,380 ‡ 1% 1% 11% 12% 7% 35 14% 23% 49% 71% 77%
Nebraska 614 2% * 0% 31% 59% 0% 51 6% 0% 12% 90% 0%
Nevada 288 1% 2% 2% 5% 3% 13 15% 23% 15% 62% 46%
New Hampshire 171 0% 9% 20% 42% 2% 51 0% 20% 22% 71% 6%
New Jersey 1,492 * 0% 9% 9% 19% 0% 142 0% 30% 8% 65% 0%
New Mexico 468 ‡ * 0% 1% 11% 16% 0% 34 ‡ 3% 12% 68% 76% 0%
New York 2,776 ‡ 8% 13% 23% 28% 0% 332 ‡ 2% 23% 61% 72% 1%
North Carolina 3,185 * 0% 3% 8% 25% 0% 215 4% 19% 19% 69% 0%
North Dakota 483 0% * 0% 4% 9% 0% 26 0% 4% 8% 85% 0%
Ohio 2,987 ‡ * 0% 7% 9% 80% 15% 293 ‡ * 0% 34% 6% 62% 73%
Oklahoma 632 ‡ * 0% 3% 42% 72% 0% 104 ‡ * 1% 6% 18% 90% 0%
Oregon 635 0% 1% 23% 28% 3% 72 0% 6% 38% 79% 26%
Pennsylvania 7,770 ‡ * 0% 2% 8% 9% 3% 401 ‡ 2% 27% 44% 68% 31%
Rhode Island 244 4% 4% 12% 19% 0% 24 42% 29% 54% 71% 0%
South Carolina 2,203 * 0% 2% 8% 16% 0% 159 0% 13% 50% 83% 1%
South Dakota 627 0% * 0% 25% 47% 0% 27 0% 0% 11% 89% 0%
Tennessee 1,168 ‡ 2% 2% 19% 22% 2% 154 ‡ 6% 8% 64% 79% 6%
Texas 4,580 * 0% 1% 15% 48% 0% 641 * 0% 3% 15% 89% 1%
Utah 1,006 0% * 0% 5% 9% 0% 35 0% 6% 37% 89% 6%
Vermont 128 1% 20% 51% 47% 0% 32 0% 72% 41% 25% 0%
Virginia 1,131 * 0% 3% 19% 19% 2% 147 1% 24% 53% 59% 16%
Washington 1,474 * 0% 0% 12% 13% 0% 50 0% 0% 76% 78% 0%
West Virginia 5,072 * 0% * 0% 7% 8% 0% 101 3% 2% 82% 93% 4%
Wisconsin 783 0% 15% 61% 56% 0% 130 0% 88% 47% 12% 1%
Wyoming 1,572 0% 0% 4% 5% 0% 22 0% 0% 18% 91% 0%

† A facility was considered likely to discharge N or P based on the presence of N or P monitoring data from facilities with its code, and the median N or P concentration in effluents discharged by facilities with its code (see information in sections below for more information).
* 0% represents a non-zero percentage of facilities which is less than 0.5%. These values can be found in the Excel download.
‡ Indicates that a state has a percentage of facilities with TIN limits : AL – 0.1% of all facilities and 2.6% of major facilities; AR – 0.4% of all facilities and 2.9% of major facilities; CA – 3% of all facilities and 13% of major facilities; CO – 0.1% of all facilities and 2.6% of major facilities; FL – 0.1% of all facilities; ID – 0.2% of all facilities; KS – 0.1% of all facilities and 1.9% of major facilities; NM – 0.2% of all facilities and 2.9% of major facilities; MO – 0.1% of all facilities and 1.2% of major facilities, MT – 0.2% of all facilities; OH – 0.2% of all facilities and 0.7% of major facilities, OK – 0.2% of all facilities and 1.0% of major facilities, TN – 0.3% of all facilities and 1.3% of major facilities; NY – 0.1% of all facilities and 0.3% of major facilities; PA – 0.2% of all facilities and 3.2% of major facilities

Source: The EPA's Permit Compliance System (PCS) and Integrated Compliance Information System - National Pollutant Discharge Elimination System (ICIS-NPDES).

Data were retrieved July 2012 for the 2010–2011 reporting year.

Download the npdesdata.xlsx(2 pp, 25 K)

Top of Page


Sources of data
1. U.S. EPA. Integrated Compliance Information System (ICIS) and Permit Compliance System (PCS) databases, from the 2010-2011 review period.
2. U.S. EPA. Facility Registry System.
3. Maupin, M.A. and T. Ivahnenko. 2011. Nutrient Loadings to Streams of the Continental United States from Municipal and Industrial Effluent. Journal of the American Water Resources Association (JAWRA). Vol 47, Issue 5, pp. 950-964.
4. U.S. Census Bureau. North American Industry Classification System.

Data source information
This indicator provides National Pollutant Discharge Elimination System (NPDES) permit information from EPA’s Permit Compliance System (PCS) and Integrated Compliance Information System – National Pollutant Discharge Elimination System (ICIS-NPDES) databases, as obtained by EPA staff from the data warehouses Envirofacts and ICIS-COPY, respectively. Data are from the 2010–2011 review period. Users can obtain data from these warehouses via the Discharge Monitoring Report (DMR) Pollutant Loading Tool.

Standard Industrial Classification (SIC) code information was used to identify facilities that are likely to discharge nitrogen or phosphorus. SIC code information was retrieved from PCS, ICIS-NPDES or EPA’s Facility Registry System (FRS). When SIC code information was not available for a permit in any of these sources, infilling procedures included applying SIC code corrections from USGS (Maupin and Ivahnenko, 2011), assigning an SIC code based on a North American Industry Classification System (NAICS) code, and assigning an SIC code of 4952 to all Publically-Owned Treatments Works (POTWs). To be flagged as likely to discharge nitrogen or phosphorus, a facility’s SIC code had to meet the following criteria:

  • Facilities with this SIC code have TN or TP monitoring data for 2007 through 2010,
  • Using data from 2007-2010, the median nitrogen concentration in effluents discharged by facilities with this SIC code is > 1.0 mg/L or the median phosphorus concentration is > 0.2 mg/L, and
  • More than 10% of all the facilities with this SIC code have monitoring data for TN or TP.

What to consider when using these data
This indicator does not include information for facilities with permit limits and monitoring requirements for other nitrogen species (i.e., total Kjeldahl nitrogen and dissolved organic nitrogen) or phosphorus species (i.e., phosphate). The data presented in this indicator are entered by permitting authorities into ICIS-NPDES or PCS either electronically or manually, and filing manually may lead to data-entry errors. Permitting authorities may not enter monitoring requirements or permit limits for minor facilities, and furthermore, if a permitting authority is delayed in entering permit facility and discharge information into ICIS-NPDES or PCS, that information would not be reflected in this dataset.

References and links to other data sources
1. SIC Codes Likely to Discharge N or P

2. Chesapeake Bay Program. 2004.  NPDES Permitting Approach for Discharges of Nutrients in the Chesapeake Bay Watershed.

3. U.S. EPA. NPDES program: Municipalities and Wastewater Treatment Plants.

4. U.S. EPA. Discharge Monitoring Report Pollutant Loading Tool.

5. U.S. EPA. Envirofacts.

6. U.S. EPA. ECHO: Enforcement and Compliance History Online.

7. U.S. Department of the Interior. National Atlas: NPDES wastewater treatment plant mapping.

Top of Page